I'm using the puppet tool to create a bird flying, and its all fine on the wing on the left, but how do I mirror the keyframes so the other wing has a duplicate movement. I tried pasting the keyframes onto the other puppet pin path for the right wing but as expected it gave me a completely different animation. Is there a short technique that allows you to have the same animation of an object at the same time on both sides. Please help.
I'm not sure if I've understood your problem correctly, because the best way to reach this may vary from the angle of the camera.
If the bird is seen from above, then you should:
1 - Precompose the wing (right click on the layer -> precompose) and go in the new tab it has created.
2 - animate the wing on its way down.
3 - use the expression (Alt + click on the watch) loopOut('pingpong') for each of the pins' value. The wing can now move for ever (but the first and the last keyframe of each pin must be at the exact same position in the timeline).
4 - Duplicate (Ctrl + D) your wing composition in the main comp.
5 - Make it 3D (click in the empty box below the cube symbol)
6 - Rotate it 180° on the Y axis and move it to the appropiate spot.
7 - In the timeline, move the duplicated wing to the end of the two animated keyframes, in order to start this animation when the other wing is half way to his mouvement.
If the bird is from a lateral angle, it will be the same process, but you'll have to rotate the new layer 180° on the X axis. In the layer panel, you'll also have to move the duplicated layer below the layer of the body, in order to hide it.